The field of art to which this invention pertains is coating compositions which cure at ambient temperatures.
Coating compositions which cure under ambient conditions have been known for a long time. The earliest of such coating compositions are coatings based on drying oils which cure by air oxidation. Other coating compositions which have been developed more recently are those based on the epoxide-carboxylic acid reaction, isocyanate-moisture reaction, polyaziridine-carboxylic acid reaction, and activated methylene-unsaturated acrylic reaction.
In U.S. Pat. No. 3,554,987, film forming interpolymers of acrylic acid, acetoacetoxyethyl methacrylate and monomers copolymerized therewith are described.
In U.S. Pat. No. 4,408,018, polymers containing pendant acetoacetate moieties are mixed with polyacrylates which contain more than one unsaturated acrylic group and are cured through Michael addition using a strong base as catalyst.
Crosslinking through Michael addition is also shown in European Patent Application No. 227,454. In this patent application, compounds containing a plurality of pendant acetoacetate groups are blended with compounds containing a plurality of ethylenically unsaturated acrylic groups and are cured with the addition of a strong base or an organometallic compound.
South African Pat. No. 85-2044 describes coating compositions curable at ambient temperatures made from a composition containing a plurality of activated methylene groups and ethylenically unsaturated carbonyl groups.
In an article by A. Noomen, entitled "Ambient Temperature Curable Coatings Based on Two-Pack Binders", Organic Coatings Conference, Athens, Greece-June, 1987, coating compositions which cure through the Michael addition reaction of acetoacetate-ketimine groups and acrylic-malonate groups are discussed.
Thermosetting coating compositions based on the epoxide-carboxylic acid reaction are disclosed in U.S. Pat. Nos. 3,305,601, and 4,028,294 and European Patent Application No. 226,171.
Due to the ever increasing demand for decorative and protective coatings which will withstand a wide variety of uses and will hold up under all kinds of environmental conditions, there is continuing research in utilizing various reactants in coating compositions.